Sister chromatid exchange and nasopharyngeal carcinoma

Sister chromatid exchange (SCE) is a genetic indicator of DNA damage in mammalian cells and may afford a sensitive monitor to follow genomic instability of some individuals with fragile chromosomal diseases or malignancies. In studies on the effect of dinitrosopiperazine (DNP), aflatoxin B1 (AFB1), methyl-nitro-nitroso-guanidine (MNNG) and Epstein-Barr virus (EBV) infection on SCE in lymphocytes from nasopharyngeal carcinoma (NPC) patients, we found that: (1) the spontaneous SCEs in peripheral blood lymphocytes (PBLs) from 75 NPC patients were significantly higher than those of PBLs from 44 normal adults, 24 cord blood (CBL) specimens, and PBLs from 20 patients with chronic inflammation of the nasopharynx; (2) PBLs from NPC patients who were positive for EBV virus capsid antigen (VCA) IgA antibody had a higher SCE frequency as compared with PBLs from VCA IgA-negative NPC patients; (3) the chemical carcinogens used induced significantly higher SCEs in lymphocytes from NPC patients than in PBLs from normal adults and CBLs; (4) the mean SCEs of EBV growth-transformed CBLs increased from 5.17 to 14.12 after infection and was similar to the level of SCEs found in PBLs from the VCA IgA-positive NPC patients. The data suggest that lymphocytes of NPC patients might be more fragile than the lymphocytes of the control groups studied.